Amine functionalized poly(vinyl alcohol) can be prepared in a variety of ways. For example, vinyl acetate can be copolymerized with amine functional monomers, such as 3-(trimethylammonium)propylacrylamide chloride, followed by hydrolysis of the acetate groups to form the corresponding vinyl alcohol copolymer. Vinyl acetate can also be copolymerized with N-vinylformamide or N-vinylacetamide to produce a copolymer which upon subsequent hydrolysis forms a poly(vinyl alcohol)-copoly(vinylamine) copolymer. Other monomers which have been copolymerized with vinyl acetate include, 2-(dimethylamino)ethyl methacrylate, 2-(diethylamino)ethyl methacrylate, 2-(dimethylamino)ethyl acrylate, 3-(dimethylamino)-2,2-dimethylpropyl acrylate, 2-(diethylamino)ethyl acrylate, 4-vinylpyridine, and allylamine. This synthetic approach can be limited in some instances due to the reactivity ratios of the monomers involved, the low solubility of some amino monomers in methanol (which is the solvent most often used to produce these copolymers), the low level of incorporation of the amino monomer into the copolymer chain, and the instability of some amino-containing copolymer repeat units under the strongly basic saponification conditions.
Alternate synthetic strategies to synthesize amine functional poly(vinyl alcohol) involve the chemical modification of poly(vinyl alcohol) homopolymer or vinyl alcohol-vinyl acetate copolymer (typically containing 1-12% vinyl acetate repeat units). For example, U.S. Pat. No. 5,380,403 (Robeson et al., 1995) discloses the transacetalization of an aminoaldehyde dialkyl acetal such as 4-aminobutyraldehyde dimethyl acetal with poly(vinyl alcohol) under acid catalysis in a homogeneous aqueous system or in a heterogeneous methanol system to produce an amine modified poly(vinyl alcohol).
Amine functional poly(vinyl alcohol) has also been made by graft polymerization of poly(vinyl alcohol) with aminoalkyl methacrylate or aminoalkyl acrylate. Other examples of producing amine functional poly(vinyl alcohol) using a poly(vinyl alcohol) post-modification synthetic approach include the etherification of poly(vinyl alcohol) with epichorohydrin followed by reaction with an amine, etherification with glycidyltrimethylammonium chloride, modification with nitrile derivatives followed by hydrogenation to the corresponding amine, and Michael reaction of acrylamide followed by Hofmann degradation. However, the above strategies do not involve straightforward reactions due to processing difficulties or side reactions, such as crosslinking.
New amine functionalized vinyl alcohol polymers and methods of making them are of continuing interest because of the recognized usefulness of the materials in a number of application areas. These polymers have proven to be useful in the paper industry for the papermaking process such as sizing, paper coatings, thermal papers, ink jet paper coatings, and creping adhesives. Amine functionalized poly(vinyl alcohol) derivatives also provide enhanced performance as flocculants, thickeners, and emulsion or colloidal stabilizers to produce positively charged emulsions. They display behavior typical of polyelectrolytes and selectively adsorb to negatively charged materials such as pulp, fiber, and glass from aqueous solutions.
A variety of amine functional poly(vinyl alcohol)s are known; however the amine functional poly(vinyl alcohol)s of this invention, especially those in which piperidone or its derivatives are incorporated into the poly(vinyl alcohol) structure by cyclic ketalization, have not been reported.